eZ\Publish\Core\Repository\ContentService::updateContent PHP Method

    public function updateContent(APIVersionInfo $versionInfo, APIContentUpdateStruct $contentUpdateStruct)
    {
        $contentUpdateStruct = clone $contentUpdateStruct;
        /** @var $content \eZ\Publish\Core\Repository\Values\Content\Content */
        $content = $this->loadContent($versionInfo->getContentInfo()->id, null, $versionInfo->versionNo);
        if ($content->versionInfo->status !== APIVersionInfo::STATUS_DRAFT) {
            throw new BadStateException('$versionInfo', 'Version is not a draft and can not be updated');
        }
        if (!$this->repository->canUser('content', 'edit', $content)) {
            throw new UnauthorizedException('content', 'edit', array('contentId' => $content->id));
        }
        $mainLanguageCode = $content->contentInfo->mainLanguageCode;
        $languageCodes = $this->getLanguageCodesForUpdate($contentUpdateStruct, $content);
        $contentType = $this->repository->getContentTypeService()->loadContentType($content->contentInfo->contentTypeId);
        $fields = $this->mapFieldsForUpdate($contentUpdateStruct, $contentType, $mainLanguageCode);
        $fieldValues = array();
        $spiFields = array();
        $allFieldErrors = array();
        $inputRelations = array();
        $locationIdToContentIdMapping = array();
        foreach ($contentType->getFieldDefinitions() as $fieldDefinition) {
            /** @var $fieldType \eZ\Publish\SPI\FieldType\FieldType */
            $fieldType = $this->fieldTypeRegistry->getFieldType($fieldDefinition->fieldTypeIdentifier);
            foreach ($languageCodes as $languageCode) {
                $isCopied = $isEmpty = $isRetained = false;
                $isLanguageNew = !in_array($languageCode, $content->versionInfo->languageCodes);
                $valueLanguageCode = $fieldDefinition->isTranslatable ? $languageCode : $mainLanguageCode;
                $isFieldUpdated = isset($fields[$fieldDefinition->identifier][$valueLanguageCode]);
                $isProcessed = isset($fieldValues[$fieldDefinition->identifier][$valueLanguageCode]);
                if (!$isFieldUpdated && !$isLanguageNew) {
                    $isRetained = true;
                    $fieldValue = $content->getField($fieldDefinition->identifier, $valueLanguageCode)->value;
                } elseif (!$isFieldUpdated && $isLanguageNew && !$fieldDefinition->isTranslatable) {
                    $isCopied = true;
                    $fieldValue = $content->getField($fieldDefinition->identifier, $valueLanguageCode)->value;
                } elseif ($isFieldUpdated) {
                    $fieldValue = $fields[$fieldDefinition->identifier][$valueLanguageCode]->value;
                } else {
                    $fieldValue = $fieldDefinition->defaultValue;
                }
                $fieldValue = $fieldType->acceptValue($fieldValue);
                if ($fieldType->isEmptyValue($fieldValue)) {
                    $isEmpty = true;
                    if ($fieldDefinition->isRequired) {
                        $allFieldErrors[$fieldDefinition->id][$languageCode] = new ValidationError("Value for required field definition '%identifier%' with language '%languageCode%' is empty", null, ['%identifier%' => $fieldDefinition->identifier, '%languageCode%' => $languageCode], 'empty');
                    }
                } else {
                    $fieldErrors = $fieldType->validate($fieldDefinition, $fieldValue);
                    if (!empty($fieldErrors)) {
                        $allFieldErrors[$fieldDefinition->id][$languageCode] = $fieldErrors;
                    }
                }
                if (!empty($allFieldErrors)) {
                    continue;
                }
                $this->relationProcessor->appendFieldRelations($inputRelations, $locationIdToContentIdMapping, $fieldType, $fieldValue, $fieldDefinition->id);
                $fieldValues[$fieldDefinition->identifier][$languageCode] = $fieldValue;
                if ($isRetained || $isCopied || $isLanguageNew && $isEmpty || $isProcessed) {
                    continue;
                }
                $spiFields[] = new SPIField(array('id' => $isLanguageNew ? null : $content->getField($fieldDefinition->identifier, $languageCode)->id, 'fieldDefinitionId' => $fieldDefinition->id, 'type' => $fieldDefinition->fieldTypeIdentifier, 'value' => $fieldType->toPersistenceValue($fieldValue), 'languageCode' => $languageCode, 'versionNo' => $versionInfo->versionNo));
            }
        }
        if (!empty($allFieldErrors)) {
            throw new ContentFieldValidationException($allFieldErrors);
        }
        $spiContentUpdateStruct = new SPIContentUpdateStruct(array('name' => $this->nameSchemaService->resolveNameSchema($content, $fieldValues, $languageCodes, $contentType), 'creatorId' => $contentUpdateStruct->creatorId ?: $this->repository->getCurrentUserReference()->getUserId(), 'fields' => $spiFields, 'modificationDate' => time(), 'initialLanguageId' => $this->persistenceHandler->contentLanguageHandler()->loadByLanguageCode($contentUpdateStruct->initialLanguageCode)->id));
        $existingRelations = $this->loadRelations($versionInfo);
        $this->repository->beginTransaction();
        try {
            $spiContent = $this->persistenceHandler->contentHandler()->updateContent($versionInfo->getContentInfo()->id, $versionInfo->versionNo, $spiContentUpdateStruct);
            $this->relationProcessor->processFieldRelations($inputRelations, $spiContent->versionInfo->contentInfo->id, $spiContent->versionInfo->versionNo, $contentType, $existingRelations);
            $this->repository->commit();
        } catch (Exception $e) {
            $this->repository->rollback();
            throw $e;
        }
        return $this->domainMapper->buildContentDomainObject($spiContent, $contentType);
    }